Pin-type synchronizer

ABSTRACT

A pin-type, double-acting synchronizer mechanism (10) with friction rings (26, 46 and 28, 48), jaw members (30, 38 and 32, 40) axially secured together by retainers (44), three circumferentially spaced pins (50) including blocker shoulders for preventing asynchronous engagement of the jaw clutches, and pre-energizer assemblies (52) to ensure initial engagement of the friction rings and blocker shoulders in response to initial engaging movement of a shift flange (42), and self-energizing ramps (20a-20d and 62a-62d). The synchronizer includes improved jaw members and self energizing ramps, an improved shift flange, improved pre-energizers, and improved jaw member retainers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. application Ser. Nos. 08/714,730;08/714;731; 08/714,732 and 08/715,262, all filed Sep. 16, 1996. All ofthese applications are assigned to the assignee of this application.

FIELD OF THE INVENTION

This invention relates to improvements of a pin-type synchronizer for atransmission.

BACKGROUND OF THE INVENTION

It is well known in the multiple speed ratio transmission art thatsynchronizer mechanisms may be used to reduce shift time of all or someof the transmission gear ratios. It is also known that the shift effortrequired by a vehicle operator, i.e., force applied to a shift lever,may be reduced by use of synchronizer mechanisms of the self-energizingtype. Since operator shift effort generally increases with vehicle size,synchronizer mechanisms of the self-energizing type are especiallyimportant for heavy duty trucks. Prior art examples of synchronizersthat are relevant to the synchronizer herein may be seen by reference toU.S. Pat. Nos. 5,078,244; 5,092,439 and 5,339,936 which are incorporatedherein by reference.

SUMMARY OF THE INVENTION

An object of this invention is to provide pin-type synchronizer havingself-energizing and an improved shift flange.

According to the invention, a pin-type synchronizer includes a pin-typesynchronizer selectively operative to frictionally synchronize andpositive connect either of first and second drives mounted for relativerotation about an axis of a shaft. The synchronizer includes first andsecond jaw members affixed respectively to the first and second drivesand respectively engagable with axially movable third and fourth jawmembers positioned between the drives. The third and fourth jaw membershave internal splines slidably mating for non-relative rotation withexternal splines affixed to the shaft. First and second cone frictionrings are respectively secured for rotation with the first and seconddrives. Third and fourth cone friction rings are concentric to the shaftand axially movable between the drives for frictional engagementrespectively with the first and second friction rings to provide asynchronizing torque for synchronizing the drives with the shaft. Aradially extending flange has axially oppositely facing sides positionedbetween the third and fourth jaw members and between the third andfourth friction rings for axially moving the jaw members and rings intosaid engagement in response to an axial bidirectional shift force F_(o)applied to the flange. Blocker means are operative when engaged forpreventing engagement of the jaw members prior to the synchronizing. Theblocker means including a plurality of circumferentially spaced apartpins rigidly extending axially between the third and fourth frictionrings and into a first set of openings in the flange. Each of the pinshas a blocker shoulders engagable with a blocker should defined aboutthe associated opening. First means secure the flange against axialmovement relative to the third and fourth jaw members. Second meansallow limited circumferential movement of the flange relative to thethird and fourth jaw members and the shaft. The second means includefirst and second ramps respectively affixed against axial and radialmovement relative to the flange and shaft. Said first and second rampsare engagable in response to the synchronizing torque for producing anaxial additive force F_(o) on the flange in the direction of the shiftforce (F_(s)) for increasing the total force engaging the frictionrings.

The improvement is characterized by the flange including an annularstiffener ring extending axially from at least one axially facing sideof the flange for reducing axial distortion of the flange duringmanufacture and while in use.

BRIEF DESCRIPTION OF THE DRAWINGS

The self-energizing synchronizer mechanism of the invention is shown inthe accompanying drawings in which:

FIG. 1 is a sectional view of a somewhat schematically illustrateddouble-acting synchronizer mechanism in a neutral position;

FIG. 2 is the synchronizer of FIG. 1 engaged rightward;

FIG. 3 is a detailed exploded view of parts of the synchronizer in FIG.1;

FIG. 4 is a detailed view of the portion of a shaft in FIG. 1;

FIG. 5 is a sectional view of the shaft in FIG. 5 and looking along line5--5 of FIG. 4;

FIGS. 6 and 7 are views of a portion of the shaft in FIG. 4 lookingalong line 6--6 of FIG. 4 and having mating self-energizing ramps ofFIG. 3 added thereto; and

FIG. 8 is a graphical representation of axial forces and torques actingon a shift flange of the synchronizer;

DETAILED DESCRIPTION OF THE DRAWINGS

The term "synchronizer clutch mechanism", used herein, shall designate aclutch mechanism utilized to non-rotatably couple a selected ratio gearto a shaft by means of a positive clutch in which attempted engagementof the positive clutch is prevented until members of the positive clutchare brought to substantially synchronous rotation by a synchronizingfriction clutch associated with the positive clutch. The term"self-energizing" shall designate synchronizer clutch mechanism whichincludes ramps or cams or the like to increase the engaging force of thesynchronizing clutch in proportion to the synchronizing torque of thefriction clutch.

Looking now at the drawings, therein is shown a gear and synchronizerassembly 10 including a shaft 12 to be mounted for rotation in atransmission about an axis 12a, axially spaced apart drives or gears 14,16, and a double-acting synchronizer 22.

The shaft 12 includes cylindrical surfaces 12b, 12c rotatably supportingthe gears thereon and an annular member 12d having an outercircumference greater in diameter than the diameters of the cylindricalsurfaces. The annular member has an axial length separating the gearsvia axially oppositely facing shoulders 12e, 12f which limit axialmovement of the gears toward each other. Axial movement of the gearsaway from each other is limited in any of several known manners. Theannular member may be formed of a ring affixed to the shaft or, asherein, formed integral with the shaft. The outer circumference of theannular member includes external splines 12g formed therein and threerecesses 18 of axial length equal to the axial length of the annularmember and self-energizing ramps 20a, 20b, 20c, 20d, explained furtherhereinafter. The recesses totally remove several adjacent splines 12g,thereby simplifying machining of the self-energizing ramps.

The synchronizer mechanism 22 includes friction rings 26, 28 and jawmembers 30,32 integrally formed with gears 14, 16, jaw members 34,36having internal spline teeth 38,40 slidably mating with the externalspline teeth 12g formed in the outer circumference of annular member12d, a radially extending shift flange 42 having axially oppositelyfacing sides 42a, 42b sandwiched between axially facing surfaces 34a,36a of the jaw members 34, 36, three axially extending retainers 44 forsecuring the flange and jaw members against relative axial movement,annular friction rings 46, 48 rigidly secured together by threecircumferentially spaced apart pins 50 extending axially from each ofthe friction members and through openings 42c in the flange, and threepre-energizer assemblies 52. Assemblies 52 are shown only in FIG. 3.

The friction rings have cone friction surfaces 26a, 46a and 28a, 48athat engage for frictionally synchronizing the gears to the shaft priorto engagement of the jaw members. Rings 46, 48 include threecircumferentially spaced and axially opening recesses 46b, 48b elongatedin the circumferential direction, and six circumferentially spaced andradially inwardly opening recesses 46c, 48c extending axially throughfriction ring 46, 48. The extra recesses 46c, 48c facilitateinterchangeability of friction rings 46, 48. As explained furtherthereinafter, recess 46b, 48b receive ends of the pre-energizerassemblies and recess 46c, 48c receive retainers 44. A wide range ofcone angles may be used; cone angles of seven and one-half degrees areemployed herein. The friction surfaces 46a, 48a and/or 26a, 28a may bedefined by any of several known friction materials affixed to the basemember; herein, pyrolytic carbon friction materials, such as disclosedin U.S. Pat. Nos. 4,700,823; 4,844,218; and 4,778,548, are preferred.These patents are incorporated herein by reference.

Pins 50 each include major diameter portions 50a having diametersslightly less than the diameter of flange openings 42c, a reduceddiameter or groove portion 50b spaced between friction rings 46, 48(herein midway), and conical blocker shoulders or surfaces 50c, 50dextending radially outwardly from the pin axis and axially away fromeach other at angles relative to a plane normal to the pin axis. Thegrooved portions, when disposed within their respective flange openings,allow limited rotation of the rigid friction ring and pin assemblyrelative to the flange to effect engagement of the pin blocker shoulderswith chamfered blocker shoulders defined about the flange openings 42c.The pins are secured to friction rings 46, 48 in any of several knownmanners.

The pre-energizer assemblies 52 are of the split pin-type shown anddescribed more completely in previously mentioned U.S. Pat. No.5,339,936. Each pre-energizer assembly extends axially between thefriction rings 46, 48 and through opening 42d which are alternatelyspaced between opening 42c. Each pre-energizer assembly, shown only inFIG. 3, includes two identical shells 54, at least two identical leafsprings 56 sandwiched between and biasing the shells apart, tworetainers 58 which telescope over ends 56a of the springs, and oblongcup-like members 60 disposed in the oblong recesses 46b, 48b in eachfriction ring 46, 48. The oblong cup-like members 60 and the recesses46b, 48b are elongated in the circumferential direction of the frictionrings and are of sufficient diameter in the radial direction of thefriction rings to allow sliding movement of opposite ends 54a of theshells 54. Each pair of shells 54 has a major diameter less than thediameter of its associated opening 42d when squeezed together,semi-annular grooves 54b with chamfered end surface 54c and the ends54a. As is known, ends 54a react against friction rings 46, 48 andchamfers 54c react against chamfers about opening 42d in flange 42 inresponse to initial engaging movement of flange 42. The cup-like members60 rigidly interface between friction rings 46, 48 and the ends 54a toprovide a wear resistant material therebetween. For example the cup-likemembers may be made of steel and the friction rings may be made ofaluminum or some other relatively soft material.

As previously mentioned, jaw members 34, 36 include internal splineteeth 38, 40 slidably mating with external spline teeth 12d affixed tothe shaft. The external splines have flank surfaces extending parallelto the shaft axis, and the mating thereof with flank surfaces of the jawmember splines prevents relative rotation therebetween.

Flange 42 further includes annular stiffener rings 42e, 42f extendingaxially from opposite sides thereof and self-energizing teeth 62projecting radially inward into the recesses 18 in the outercircumference of shaft annular member 12d. Each tooth 62 includesself-energizing surfaces 62a, 62b, 62c, 62d which cooperate or reactagainst the self-energizing ramp surfaces 20a, 20b, 20c, 20d,respectively. Each stiffener ring includes a radially inwardly facingsurface 42h receiving a annular radially outwardly facing surface 34c,36c of the jaw members 34, 36. The stiffener rings reduce axialdistortion of flange 42 during manufacture and while in use. The rampsurfaces allow limited rotation of the flange relative to jaw members34, 36 and shaft 12, and react synchronizing torque between the coneclutches and shaft to provide an additive axial self-energizing forcefor increasing the engaging force of the cone clutch initially engagedby a shift force applied to flange 42, thereby increasing thesynchronizing torque provided by the cone clutch. The ramp surfaces maybe provided for increasing synchronizing force for one or both gearsand/or for increasing synchronizing force in response to torque ineither direction, as is encountered for up and down shifts.

The retainers 44 each include an axially extending portion 44a disposedabout radially outward portions 34b, 36b of jaw members 34, 36 andaxially spaced apart and radially inwardly extending portions 44bembracing axially oppositely facing portions 34b', 36b' of jaw members34, 36. The retainers loosely extend through opening 42c in flange 42for allowing limited relative rotation therebetween. Each axiallyextending portion has axially spaced apart and radially outwardly facingportions 44c received in friction ring recesses 46c, 48c and inrelatively close sliding relation with radially inwardly facing portionsof the recesses. Portions 44c are long enough to remain in slidingrelative with the inwardly facing portions of the recesses. Gears 14, 16include axially extending recesses 14a, 16a for receiving end portionsof the retainers when the jaw members are engaged. See FIG. 2. Theradially extending sides of recesses 46c, 48c maintain circumferentialspacing of the retainers. Ramp surfaces 20a,20b affixed to shaft 12respectively react against ramp surfaces 62a, 62b on flange teeth 62 toprovide additive axial forces to increase or assist the synchronizationrate and/or shift quality of gear 16 in response to torque in eitherdirection. Ramp surfaces 20c, 20d respectively react against rampsurfaces 62c, 62d to provide the additive axial forces for gear 14 inresponse to synchronizing torque in either direction. The angles of theramp surfaces may be varied to provide different amounts of additiveaxial force for up and down shifts and for high and low speed ratios.Also, if no additive axial force is preferred in one direction for onegear or more, the ramp surfaces may be parallel to the shaft axis, i.e.,no effective ramp surfaces are provided. The magnitude or amount of theaxial additive forces, as explained further hereinafter, is also afunction of the mean radii ratio of friction clutches andself-energizing ramps. Accordingly, the magnitude of the additive forcesfor a given shift force applied to shift flange 42 by a shift fork maybe varied by varying the ramp angles and/or the mean radii ratio.

When the flange 42 is in the neutral position of FIG. 1, reduceddiameter portions 50b of pins 50 are radially aligned with theirassociated flange openings 42c, friction surfaces of the cone clutchesare slightly spaced apart and are maintained in this spaced relation bychamfered or angled pre-energizer surfaces 54c of the pre-energizers 52acting on pre-energizer chamfered surfaces about flange openings 42d bythe force of springs 56. The axial force provided by the pre-energizersurface is preferably sufficient to counter act any additive axial forceon flange 42 by the self-energizing ramps due to viscous shear of oilbetween the cone clutch surfaces. When it is desired to couple eithergear to the shaft, an appropriate and unshown shift mechanism, such asdisclosed in U.S. Pat. No. 4,920,815 and incorporated herein byreference, is connected to the outer periphery of flange 42 in knownmanner for moving the flange axially along the axis of shaft 12 eitherleft to couple gear 14 or right to couple gear 16. The shift mechanismmay be manually moved by an operator through a linkage system, may beselectively moved by an actuator, or may be moved by means whichautomatically initiate shift mechanism movement and which also controlsthe magnitude of the force applied by the shift mechanism. When theshift mechanism is manually moved, the force is proportional to theforce applied by the operator to a shift lever. Whether manually orautomatically applied, the force is applied to flange 42 in an axialdirection and is represented by the length of arrow F_(o) in FIG. 7.

Initial rightward axial movement of flange 42 by the operator shiftforce F_(o) is transmitted to pins 50 by pre-energizer surfaces 54c toeffect initial frictional engagement of cone surface 48a with conesurface 28a. The initial engagement force of the cone surface is ofcourse a function of the force of springs 56 and the angles of thepre-energizer surfaces. The initial frictional engagement (provided anasynchronous condition exists and momentarily ignoring the effect of theself-energizing ramps) produces an initial cone clutch engaging forceand synchronizing torque T_(o) which ensures limited relative rotationbetween flange 42 and the engaged friction ring, and hence, movement ofthe reduced diameter pin portions 50b to the appropriate sides of theflange openings 42c to provide engagement of pin blocker shoulders 50dwith the blocker shoulders disposed about openings 42c. When the blockershoulders are engaged, the full operator shift force F_(o) on flange 42is transmitted to friction ring 48 via the blocker shoulders, wherebythe cone clutch is engaged by the full force of the operator shift forceF_(o) to provide a resultant operator synchronizing torque T_(o). Thisoperator synchronizing torque T_(o) is represented by arrow T_(o) inFIG. 8. Since the blocker shoulders are disposed at angles relative tothe axial direction of operator shift force F_(o), they produce acounter force or unblocking torque which is counter to the synchronizingtorque from the cone clutch but of lesser magnitude during asynchronousconditions. As substantial synchronism is reached, the synchronizingtorque drops below the unblocking torque, whereby the blocker shouldersmove the pins into concentric relation with openings 42c to allowcontinued axial movement of the flange and engagement of the internalspline/jaw teeth 40 of jaw member 36 with external spline/ jaw teeth ofjaw member 32, as shown in FIG. 2. The spline/jaw teeth may beconfigured as shown in U.S. Pat. Nos. 3,265,173 and 4,246,993 which areincorporated herein by reference.

Still ignoring the effects of the self-energizing ramps, cone clutchtorque provided by the force F_(o) is expressed by equation (1).

    T.sub.o =F.sub.o R.sub.c μ.sub.c / sin α          (1)

where:

R_(c) =the mean radius of the cone friction surface,

μ_(c) =the coefficient of friction of the cone friction surface, and

α=the angle of the cone friction surfaces.

Looking now at the affects of the self-energizing ramps and referringparticularly to FIGS. 6 and 7, the synchronizing torque T_(o), due tothe operator applied axial shift force F_(o), is of course transmittedto flange 42 by pins 50 and is reacted to shaft 12 across theself-energizing ramp surfaces. The self-energizing ramp surfaces, whenengaged, limit rotation of the flange relative to shaft 12 and jawmembers 34, 36, and produce an axial force component or axial additiveforce F_(a) acting on the flange in the same direction as shift forceF_(o), which forces sum to provide a total force F_(t), thereby furtherincreasing the engaging force of the cone clutch to provide an additivesynchronizing torque T_(a) to provide a total torque T_(t) which adds tothe torque T_(o). FIG. 6 illustrates the position of the self-energizingramp surfaces while shift flange 42 is in the neutral positioncorresponding to the position of FIG. 1. FIG. 7 illustrates a positionof the ramps and splines while gear 16 is being synchronized by engagedcone surfaces 28a, 48a. The engaged cone surfaces are producing asynchronizing torque in a direction which has effected engagement offlange ramp surfaces 62a with shaft ramp surfaces 20a. Hence, the sum ofthe axial forces for engaging the cone clutch are F_(o) plus F_(a) andthe sum of the synchronizing torques being produced by the cone clutchare T_(o) plus T_(a), as graphically shown in FIG. 8. For a givenoperator shift force F_(o) and an operator synchronizing torque T_(o),the magnitude of the axial additive force is preferably a function ofthe angle of the engaged self-energizing ramp surfaces. This angle ispreferably great enough to produce an additive force F_(a) of magnitudesufficient to significantly increase synchronizing torque and decreasesynchronizing time in response to a given moderate shift effort by theoperator. However, this angle is also preferably low enough to produce acontrolled axial additive force F_(a), i.e., the force F_(a) shouldincrease or decrease in response to the force F_(o) increasing ordecreasing. If the ramp angle is too great, the ramps are self-lockingrather than self-energizing; hence, once initial engagement of the coneclutch is effected the force F_(a) will rapidly and uncontrollablyincrease independent of the force F_(o), thereby driving the cone clutchtoward uncontrolled lockup. Self-locking rather than self-energizingdecreases shift quality or shift feel, may over stress synchronizercomponents, may cause over heating and rapid wear of the cone clutchsurfaces, and may even override operator movement of the shift lever.

The main variables and equations for calculating self-energizing rampangles may be seen by reference to previously mentioned U.S. Pat. No.5,092,439.

A preferred embodiment of a pin-type synchronizer has been disclosed.The following claims are intended to cover inventive portions of thedisclosed sychronizer and variations and modifications believed to bewithin the spirit of the invention.

What is claimed is:
 1. A pin-type synchronizer selectively operative tofrictionally synchronize and positive connect either of first and seconddrives mounted for relative rotation about an axis of a shaft; thesynchronizer including:first and second jaw members affixed respectivelyto the first and second drives and respectively engagable with axiallymovable third and fourth jaw members positioned between the drives, thethird and fourth jaw members having internal splines slidably mating fornon-relative rotation with external splines affixed to the shaft; firstand second cone friction rings respectively secured for rotation withthe first and second drives and third and fourth cone friction ringsconcentric to the shaft and axially movable between the drives forfrictional engagement respectively with the first and second frictionrings to provide a synchronizing torque for synchronizing the driveswith the shaft; a radially extending flange having axially oppositelyfacing sides positioned between the third and fourth jaw members andbetween the third and fourth friction rings for axially moving the jawmembers and rings into said engagement in response to an axialbidirectional shift force applied to the flange; blocker means operativewhen engaged for preventing engagement of the jaw members prior to thesynchronizing, the blocker means including a plurality ofcircumferentially spaced apart pins rigidly extending axially betweenthe third and fourth friction rings and into a first set of openings inthe flange, each of the pins having a blocker shoulder engagable with ablocker shoulder defined about the associated opening; first meanssecuring the flange against axial movement relative to the third andfourth jaw members; second means allowing limited circumferentialmovement of the flange relative to the third and fourth jaw members andthe shaft, the second means including first and second rampsrespectively affixed against axial and radial movement relative to theflange and shaft, said first and second ramps engagable in response tothe synchronizing torque for producing an axial additive force (F_(a))on the flange in the direction of the shift force for increasing thetotal force engaging the friction rings; the improvement comprising: theflange including an annular stiffener ring extending axially from atleast one axially facing side of the flange.
 2. The synchronizer ofclaim 1, wherein:the annular stiffener ring includes a radially inwardlyfacing surface receiving an annular radially outwardly facing surface ofthe third jaw member.
 3. The synchronizer of claim 1, wherein:the flangeincluding another annular stiffener ring extending axially from anotheraxially facing side of the flange.
 4. The synchronizer of claim 3,wherein:the annular stiffener ring includes a radially inwardly facingsurface receiving an annular radially outwardly facing surface of thethird jaw member.